Water-borne craft with rotatable float bodies

ABSTRACT

A water-borne craft having at least two parallel rotatable float bodies, the general cylindrical form of which has at least two helicoidal turns which extend from the front end to the rear end and around an imaginary or actual central hub and which between them form two passages progressively diminishing in depth from the front end of the float body to the rear end.

ilnited States Patent 11 1 Justinien Sept. 23, 1975 1 WATER-BORNE CRAFT WITH 1426,721 2/1969 .lustinien 115/19 ROTATABLE FLOAT BODIES FOREIGN PATENTS OIR APPLICATIONS [76] Inventor: Marcel J ustinien, 20 bis u 2009.038 9/1970 Germany 16 115/19 Jouvenent, 75016 Paris, France 1 460517 10/1966 France w 115 19 22 P] d: M 14,1974 l l C ay Primary ExaminerTrygve Ml. 811K [21] Appll No.2 469,843 Assistant ExaminerCharles E. Frankfort Attorney, Agent, or FirmLa1ne, Aitken. Dunner & [30] Foreign Application Priority Data Zlems 197 1 May 18, 3 France 7318812 ABSTRACT 52 US. Cl 115/19; 416/176 A water-borne Craft having at least two Parallel rotat- 51 lm. c1. B63H 1/12 able float b0die$- the general Cylindrical form of which [53] Field of Search 115 19 20 1 41 17 has at least two helicoidal turns which extend from the 416/g4 85 177; 415/72 front end to the rear end and around an imaginary or actual central hub and which between them form two [56] References Ci d passages progressively diminishing in depth from the UNITED STATES PATENTS front end of the float body to the rear end.

2,388,711 11/1945 Sawyer 115/19 9 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 2 3,906,888

US Patent Sept. 23,1975 Sheet 2 01 2 3,906,888

WATER-BORNE CRAFT WITH ,ROTATABLE FLOAT BODIES BACKGROUND OF THE INVENTION It is known that rotatable cylindrical floats have hith- 5 jecting peripheral turns.

SUMMARY OF THE INVENTION According to the present invention, all the submerged surfaces, not parallel with the axis of the rotatable float body, are integrally helicoidal. By virtue of this, the article of the invention is even superior to the best conventional screws, the pitch of the blades of which is not the same around the axis and at the maximum radius. There thus result resistance and a screw efficiency that varies between 50 to 60%. The floating screw of the invention supports the actual sea-borne craft which is above the water. The draught of the hull screw does not exceed one quarter of its diameter when under full load and when ready to travel. This results in: a

l. a great buoyancy reserve, and

2. no pitch resistance.

The integrally helicoidal character of the rotatable float bodies offers the advantage of enabling great speeds to be attained since the kinetic energy automatically passes from forward to aft at a rate strictly equal to the speed of displacement. Thus, there are no bow waves, dynamic displacement of water or wake (suction).

This integrally helicoidal character of the float bodies of the invention is obtained by the fact that, both at the rear and at the front, the helicoidal development of the turns or screw threads begins and terminates at the-full diameter of the float. The starting plane of the turns is a vertical plane both at the frontand the back, this plane being perpendicular to the general longitudinal axis of the float.

In the known forms of rotatable floats, the development of the turns and therefore of the passages that will be discussed later herein does not occur over a vertical plane but over an inclined plane, the slope of which varies with the length of pitch. The helicoidal develop ment thus occurs simultaneously with the spiroidal development. This results, at the front, in a great increase in volume from front to rear, which the helicoidal nature does not completely correct, whereas at the rear the situation is reversed.

BRIEF DESCRIPTION OF THE DRAWINGS Some embodiments of the invention will now be described by way of example and by reference .to the annexed drawings in which: w

FIG. l is an exterior longitudinal side view of a rotatable float body in accordance with the invention.

FIG. 2 is a front end-view of the float bodyvof FIG. I shown in two developed forms.

FIG. 3 is a rear end-view of the float body of FIG. 1.

FIG. 6 shows on a larger scale a cross-section through a helicoidal propelling fin of the rotatable float body.

FIG. 7 shows a water-borne craft equipped with rotatable float bodies in accordance with one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The characteristics of the integrally helicoidal rotat able float body of the invention are as follows:

The helicoidal development of the turns or screw threads of the float body begins and ends at the full diameter D of the float. The latter is reached after spiroidal development which occurs in the vertical plane and over a minimum distance of 165. 8

I The plane in which the turns begin at the front and at the rear is a vertical plane perpendicular to the general longitudinal axis x-x of the float.

The turns number at least two, and there may be 10 of them or even 12 in the case of floats intended for use on high-tonnage water-borne craft.

When the turn has reached the maximum radius of development, a passage 1 is formed between the imaginary or actual central hub 2, the maximum diameter d of which is approximately equal to one-third of the diameter D of the float, and the maximum radius R of the float.

To give a non-limiting example, if the diameter D of the float is 2 metres, the diameter d of the central hub at which the turns begin is 55 to 60 cm. I

Consequently in the latter case (60 cm), the waterline (one-fourth of the diameter, i.e. 50 cm) will be 20 cm below the central hub and that the passage will then have a depth of cm.

In fact, taking into account the thicknesses and the rounded form, when the greatest radius is reached, the depth is less,

Starting from there, the passage becomes helicoidal in accordance with the definition of a conventional helix: a straight line wound round a cylinder of revolution. The angle A that this straight line forms with a horizontal line (the axis x-x) determines the pitch.

The width of the passage or passages remains unchanged to the rear end of the float and always on the same radius. There is therefore no pitch resistance, the less so since when stopped the floats will never have a draught in excess of one-fourth of the diameter D. On the other hand the depth of the passage or passages will diminish progressively and over a very great length.

The central hub 2 may be a little larger at the rear than at the front as shown in the Figures. For example if the hub has a diameter of 55 60 cm, the rear will be 70-75 cm in diameter so as to avoid dipping at the rear in certain forms of construction. The number of spiroidal passages or screw-threads is of course the same at the rear and the front.

The bottom (lla) of the passages (FIG. 4) is very much rounded to prevent any possible resistance due to turbulence, whereas that side lb of the passage that faces downwardly and rearwardly in the direction of the helicoidal line is pronouncedly convex (in the autorotating version of course), whereas the other side 16 with which the water comes into contact to cause the float to rotate has a planar surface or a substantially planar surface and is connected by a slightly rounded zone to the outer peripheral edges.

At the rear, the flank of the passage should be as convex as possible from the periphery to the central hub. The passage runs from front to rear. The exterior side of the flank terminates at the maximum radius, (it also begins at this full radius or diameter). The hollow portion 1b of the passage terminates at the rear central radius (seen from the end face, FIG. 3).

The passage continues from the complete spiroidal development (165 minimum of development), and the crest of the two flanks on each helicoidal passage is always at the maximum radius.

The width of the passages and that of the cylindrical lands that they separate are inversely proportional to their number, but the pitch remains the same. For ex-- ample, for the same pitch it is possible to have either two screw-threads, two passages and two helicoidal lands, or four lands for four turns, the lands and the passages being half as wide and the passages less deep, the shape of the passages never changing however.

In the autorotating version, the floats are not propelling means; the forward end skims the water which engulfs the passages, the helicoidal surfaces of which are streamlined like the leading edges of the blades of a conventional screw. The floats turn under the effect of the water pressure on the side 1c of each passage.

The non-driven wheels of any vehicle turn at the same speed as that of the driven wheels, assuming the diameters are the same. In effect the tangential surface of eachwheel presses on to the ground, or in the case of railway carriages, on the rails, and the adherence is very great. The same conditions do not apply in the case of integrally helicoidal floats, for the following two reasons:

a. water is a fluid and however firm the pressure it slides over the forward wall of each passage with the result that the speed of rotation of the floats cannot automatically correspond to the speed of movement of the floating craft, when pitch is taken into account;

b. when turning the surfaces encounter frictional resistance which depends mainly on the nature of the surfaces. If the surfaces are very good, that is to say very smooth, they only offer low resistance. They then represent at most 10% of the total of the conventional resistance (resistance due to pressure against the bow waves and pressure due to dynamic displacement of water and to rear suction). At the front, the visible sign of this resistance is the bow wave, and at the rear, the wake. Such resistance is not offered to the helicoidal float. On the contrary with rough surfaces the frictional resistance is appreciably greater. It is for this reason that the surface of the floats should be as smooth as possible to give the maximum efficiency.

Whatever the extent to which it occurs, this frictional resistance, also known as tangential resistance, retards rotation. Consequently the floats do not turn quite as rapidly as they should, and the helicoidal surfaces do not move under pressure from the water in the manner required. In this case there is resistance which, although not so great as that offered by the bows of a vessel, is nevertheless not inconsiderable.

In order to eliminate this resistance which also occurs at the rear, there is provided a couple which compensates this resistance. This couple, the strength of which is considerably less than the propulsive resistance, is sufficient to ensure that the floats rotate at a rate completely suited to the speed of displacement of the vessel. Propulsion is provided by one or more conventional screws or by air-screws or even turbo-jets or hydraulic turbo-jets situated, like the screws, towards the stern and between the floats. In the case of small waterborne craft of up to approximately three tons, a single motor can be used to turn the propeller screw 3 and to act as a couple, a transmission shaft 4 being connected to the floats (craft illustrated in FIG. 7 in which the floats comprise four helices). It is however advantageous to provide two motors, for example a HP. motor for the propeller screw and a 30 HP. motor for the couple, the total power being H.P., but the speed being multiplied by 1.8 because of the presence of the couple, as shown in a number of laboratory experiments and in tests on open water.

The auto-rotating version offers the advantage of permitting a very large pitch to be used (up to 3.75/4.8 times the diameter). It can also be used and is indeed necessary in the case of sail ships driven by the wind. The couple is represented either by a small auxiliary motor as provided in the majority of such vessels, or by awind-engine connected to the shafts of the floats.

To summarize, the compensating couple is indispensable for obtaining the maximum advantages from the invention. The transmission ratio of the drive for the floats as well as for the screws will be in the order of the ratio of the respective pitches of the floats and screws, with 10 to 15% more in the case of the latter because of the well-known recessional movements, though this occurs to a lesser extent than in conventional craft, the hulls of which have a very considerable retarding effect.

Numerous experiments carried out on the selfpropelling version have shown that elimination of resistance enables speed to be increased using the same power, without any offsetting disadvantages; it was however also found that it is difficult to reconcile the requirements of great speed with strong propulsion. This finding, supported by trials, proves incontestably that the problem posed by the slowness of vessels is not a problem of propulsion but that of eliminating the main causes of resistance.

Nevertheless, in the case of water-borne craft for which high speed is not important and indeed would be undesirable, and which instead require a great propulsive force, such as push-off vessels, tugs, harbourbound craft, water-buses plying on rivers and small lakes, ferries and amphibian craft, all of which have to stop frequently or require considerable power for starting up, the floats forming the subject-matter of this Application will be different from those that may be used in the auto-rotating version (see FIGS. 5 and 6).

The integrally helicoidal character of all the submerged surfaces not parallel to the longitudinal axis remains unchanged. The dimensional relationships are however different, and particularly efficient propulsive means are also provided.

The pitch will be considerably shorter, and its minimum will be a little less than the diameter, and its maximum equal to 1.9 times the diameter.

Around each float there are provided propelling fins 5 having a depth equal to one-tenth of the diameter D, these fins beginning and terminating at the maximum radius. In no case should the fins start at the central hub at the front, nor should they run back to the hub at the rear. lf the craft are for amphibious use, the fins are reinforced to permit travel over the ground. These are the craft that use the shortest pitch.

in the case of relatively slow-moving craft, the draught may slightly exceed one-fourth of the diameter, i.e. may be between one-fourth and one-third, and the latter figure should not be reached when the engine or motor is under full load and the vessel is halted.

There are as many fins as there are turns. These helicoidal fins replace the passages which terminate after approximately one halfrevolution of the helicoidal developrnentv They disappear at the point where the final passages reappear at the rear and with rapid development.

in the case of water-borne craft intended to travel at relatively high speeds, and again in the self-propelling version, the floats will not have propelling fins such as those shown at 5. The pitch will of course be shorter, but the passages will be continuous as in the autorotating version. However the more steeply inclined flank of each of these passages will face forwardly and not rearwardly. Furthermore in this case there will be advantageously provided a co-propelling couple of considerably less power than that provided for the floats and obtained for example by a small auxiliary motor driving a conventional screw.

it shouid also be stated that a maximum of two juxta posed (parallel) floats may be fitted. On the other hand there may be four floats, i.e. two on each side one behind the other, and power is preferably transmitted to the shaft connecting them. Also, the length of each float will generally not exceed a value of 6 to 7 times their diameter", in both versions. The floats arranged in this manner are hollow and may be made by any suitable known method from a great variety of materials. For example in the case of small craft they may be made of thermosetting plastics materials (polyesters or polystyrene). For larger craft, the floats may be made of a light alloy or even of steel or the like for vessels of very high tonnage. Use may also be made of light foamed plastics materials such as polyurethane or Klegecell for floats for craft manufactured in small numbers and in small sizes.

The above description will have clearly indicated the advantages of the invention the more important of which are:

increases in buoyancy without increase in volume from stem to stem, by development of the turns at the front on a vertical plane,

the compensating couple enables high speeds to be obtained with a very long pitch which, among other applications, is of interest as regards pedal-powered sailing vessels in which the pedalling mechanism acts as a compensating couple, and

the shape at the rear inhibits the intake of water and resistance to rotation which are the cause of consider able retardation.

What I claim is:

1. A water craft having at least one rotatable float body of a general cylindrical form and defined by a helical winding extending from the front end to the rear end of said body, with the helicoidal development of the winding beginning at said front end and terminating at said rear end at or substantially at the full diameter of the body in a plane substantially perpendicular to the general longitudinal axis of the body, the adjacent portions of the winding defining a passage the depth of which diminishes progressively over its entire length from said front end to said rear end.

2. A water craft according to claim 1, wherein the width of said passage is equal at all points along its length.

3. A water craft according to claim 1, wherein said winding defines a central hub which is larger at said rear end than at said front end.

4. A water craft according to claim 3, wherein said hub is about one-third larger at said rear end than at said front end.

5. A water craft according to claim 1, further comprising a drive means for propelling said craft, and means for applying a low-power compensating couple to said float body, which couple ensures an absolute relationship between the speed of rotation of the float and the speed of displacement of the craft.

6. A water craft according to claim 1, wherein the pitch of said winding is at most 3.75 to 4.8 times the diameter of said body.

7. A water craft according to claim 1, wherein the pitch of said winding is at minimum slightly less than the diameter of said body and at maximum equal to 1.9 times said diameter.

8. A water craft according to claim 1, further comprising motive means for driving said body to propel said craft.

9. A water craft according to claim 1, further comprising a plurality of helicoidal propelling fins extending over said winding, the number of fins being equal to the number of turns of said winding, said fins beginning and ending at the full diameter of said body behind said passages at said front end, and in front of said pas- 

1. A water craft having at least one rotatable float body of a general cylindrical form and defined by a helical winding extending from the front end to the rear end of said body, with the helicoidal development of the winding beginning at said front end and terminating at said rear end at or substantially at the full diameter of the body in a plane substantially perpendicular to the general longitudinal axis of the body, the adjacent portions of the winding defining a passage the depth of which diminishes progressively over its entire length from said front end to said rear end.
 2. A water craft according to claim 1, wherein the width of said passage is equal at all points along its length.
 3. A water craft according to claim 1, wherein said winding defines a central hub which is larger at said rear end than at said front end.
 4. A water craft according to claim 3, wherein said hub is about one-third larger at said rear end than at said front end.
 5. A water craft according to claim 1, further comprising a drive means for propelling said craft, and means for applying a low-power compensating couple to said float body, which couple ensures an absolute relationship between the speed of rotation of the float and the speed of displacement of the craft.
 6. A water craft according to claim 1, wherein the pitch of said winding is at most 3.75 to 4.8 times the diameter of said body.
 7. A water craft according to claim 1, wherein the pitch of said winding is at minimum slightly less than the diameter of said body and at maximum equal to 1.9 times said diameter.
 8. A water craft according to claim 1, further comprising motive means for driving said body to propel said craft.
 9. A water craft according to claim 1, further comprising a plurality of helicoidal propelling fins extending over said winding, the number of fins being equal to the number of turns of said winding, said fins beginning and ending at the full diameter of said body behind said passages at said front end, and in front of said passages at the rear end. 